As a victim of identity theft, and a fairly astute user of tech, I can advise that there are some simple steps you can take to protect your privacy on the public web. (And my ID theft happened not because of some shit I did on a website, but when the OPM database was hacked some years ago. They got my social and filed a false tax return with it. I got it straightened out within 18 months. It sucked but no real damage was done.)
For instance, Facebook. DON'T PUT YOUR REAL NAME AND BIRTHDATE IN IT!
Oh, you did already? Too bad you cannot change it. Oh well, make a new fake account, or continue to use the one with all your real information.
Did you use your REAL NAME in anything else? Oh well, too bad that the information is now in the cloud. No point in trying to change it.
Advertisers? Well, for one, just ignore advertisers. Don't click the ads. Don't feed the ad.doubleclick.net monkey.
Don't put in real information into anything you use online that is public. It is really quite simple.